The empirical studies on the effects of income tax integration policy have been largely conducted from the angle of ex ante policy simulation. However, since Taiwan has adopted income tax integration reform in 1998, ex post assessment becomes essential for further policy modification. This study evaluates the income tax reform by building up a CGE model and placing a reverse shock back to the status of no reform. Then the comparison is made between statistical reality and the estimates of no reform. The data of national income and input-output table of 1999, the year that the new income tax system was applied for the first time to business and individual incomes generated in 1998, are adopted as the benchmark equilibrium. The descriptions of income flows among different sectors and of different sources of capital financing are carefully added into the model. Business finance policy and dividends policy are endogenized. With all these new features, the impacts of the tax reform can be fully revealed.